This is kinda silly. Brainwashing doesn't work that well. He might be able to trick her into fighting strangers. There is no way the brainwashing would work once someone she recognizes is talking to her.
That's not even factoring someone who she trained with everyday and supposedly loves. Her body would remember him if not her mind. Muscle memory would simply recognize the way he takes up her space.
It's all just a way to make the two fight because the author seems to want that, even if his fans don't seem to.